The present invention relates to the field of motion picture cameras and motion picture projectors, and more particularly to optical systems for such cameras and projectors which obtain a wide angle of viewing and projection.
There has been a number of suggestions in the past for motion picture camera systems which would provide a wide angle of viewing. For example, it is possible to construct camera lenses and projection lenses which provide a viewing angle of about 50.degree. to 70.degree., although in some of these lenses there is considerable distortion near the outer edges of the viewing screen. It has also been suggested and implemented that a number of motion picture cameras may simultaneously and in synchronism take pictures with the cameras positioned to cover the entire desired wide-angle field, for example, a field of 180.degree. or 360.degree.. If the desired field is 180.degree. and each camera takes a maximum of 45.degree., then it is required to utilize four cameras whose mechanisms are operated in synchronism. Subsequently, in projection, the four separate films are projected separately each through its own projector, and the projectors arranged at an angle to each other to cover a 180.degree. screen. The projectors are run in synchronism and attempts have been made to have their images overlap to avoid the problem of lines appearing between each of the images.
In conventional motion picture projection the screen has a ratio of width to height of 1.33:1. It has been suggested that an anamorphic lens system be used in front of the conventional camera lens to produce a squeezed wide angle picture which fits into a standard 35 mm move picture frame. Another anamorphic lens is then used for projection and the film is projected on a screen having a width-height ratio of 2.66:1. That system may give a horizontal field of about 70 degrees compared to the normal field of 40.degree., but presents a squeezed image which is difficult to edit.
A different type of system is shown in the Ayres U.S. Pat. No. 2,244,235, dated June 3, 1941 entitled "Cyclormic Optical System." In the Aygres patent the image from a 360.degree. scene, having reference to the horizontal, is obtained on the bottom portion of a reflective ball element. That image is transmitted through a focusing lens and recorded on a conventional motion picture film. The image on the film, as shown in FIG. 4 of that patent, is a circle having a central aperture. The film image is distorted and would be extremely difficult, if not impossible, to edit using conventional techniques. The film image may subsequently be projected using a similar system, that is, it is projected from the film through a lens and onto a ball element. The Ayres system, in addition to its film being difficult to edit, also presents serious problems in film-making. The camera is positioned horizontally, which makes it difficult to handle using conventional film camera stands and film camera handling techniques.
A somewhat similar system is shown in U.S. Pat. No. 2,299,682 to J. S. Conant, issued Oct. 20, 1942. In the Conant system the reflective ball element, instead of being a hemisphere, is a convex parabolic reflector. The Conant patent utilized a curved screen for projection, which is a hemispherical screen or which is a small section of a relatively large diameter sphere.
In still cameras it is known that a "fisheye" lens may cover a wide angle of 180.degree. or more. However, the image is extremely distorted and in some lenses may be described as establishing the relationship between cubival angle and area size of images in equisolid angle projection. A "super wide angle lens" is available from 15 mm to 25 mm. For example, an 18 mm 3.5 lens has been announced by ZUIKO (Olympus, Tokyo, Japan) having a 100.degree. angle of view and 12 lens elements. A still camera standard wide angle lens has an angle of view of about 50.degree..